1. Field of the Invention
The present invention relates to an antenna structure of mobile phone, and particularly to an antenna structure with lower specific absorption rate (SAR).
2. The Related Art
As the development of modern mobile communication industry, mobile phones are designed more and more smaller with beautiful appearance and have better broadcasting and receiving capability. In this case, the SAR of the mobile phone becomes high and thus unacceptable by most applied regulations.
As shown in FIG. 4, a conventional antenna structure 100 includes an antenna portion 110 and a grounding portion 120. The antenna portion 110 located on the front portion of the grounding portion 120, includes a printed circuit board (PCB) 111 and an antenna 112 printed on top surface of the PCB 111. The grounding portion 120 is merely a sheet metal placed on a housing 130 of a mobile phone. The antenna 112 defines a feeding point 113 and a grounding point 114. The grounding point 114 electrically connects with the grounding portion 120 through the PCB 111.
However, because the grounding portion 120 of the conventional antenna structure 100 is in a plane type formation, the size of the grounding portion 120 is restricted by the length and width of the housing 130 of the mobile phone. Since the electric field of the conventional antenna structure 100 is focused within the limited grounding portion 120, the SAR of the conventional antenna structure 100 is therefore increased.